In an exclusive interview with Breitbart News, the son of Republican presidential nominee Donald Trump praised energy production jobs, which have kept the state afloat since the country’s late-2000s recession, as important to national security as well as economic growth.

Trump lit into Bill Clinton’s recent comments mocking coal workers. The former president called them “coal people,” said they believe global warming is a “Chinese hoax,” and taunted their work as outdated and obsolete. Breitbart News’ Charlie Spiering reported on Clinton’s remarks at a Pennsylvania rally last week:

He argued that coal workers should realize that the industry was dying and that it was time to focus on solar panels and windmills.

“Coal employment peaked in 1920, coal production peaked in 1950,” he said, adding, “Climate change is real and we’re going to have to change our energy source.”

“If there’s been a boom in Pennsylvania, it’s because of natural gas. Your Democratic governor wants to take credit for that, but guess what? Hillary Clinton wants to shut those things down. She wants to be beholden to Saudi Arabia, who writes her $25 million checks.”

Trump continued this line of attack, arguing that preserving the U.S. energy industry is a “national security” issue.

“That’s not just common sense, it’s not just energy independence, it’s not just jobs and tax base, it’s national security,” he said. “To be able to take care of ourselves and make sure we’re utilizing the resources that we’ve been blessed to have — I mean, we’re the natural gas capital of the world. And yet, she’d want to shut that down so that we can write checks to countries that hate our guts and hate our values and hate everything about us. That’s not gonna happen on our watch.”

Asked about his father’s chances of winning Pennsylvania — which has not gone to a Republican presidential candidate since 1988 — Trump touted local efforts like the Southpointe office celebrating its grand opening on Wednesday. He said a strong get-out-the-vote effort would come from “people on the ground speaking to the union voters. Yes, the union bosses, they’ve been bought and paid for by the DNC for generations. But the actual workers, the working-class men and women of this country, those are the people who are going to break party lines.

“They’re gonna come and vote for Trump, because, you know what? They want to see common sense infused back into politics, back into government. They’re sick of seeing everyone around DC and all the zip codes around DC being the richest in the country while they suffer.”